25 May
2009
25 May
'09
10:40 p.m.
I wondered what the prevalent opinion was about setting up a software
raid mirror of two sata drives under Linux LVM. This is on a 3.2GHz
quad core AMD system that almost certainly has plenty of free CPU. Will
this provide extra disk i/o that could be usefully applied to getting
more simultaneous tracks, or will using a software mirror interfere with
the RT kernel or cause latency issues/instability somewhere?
--
+ Brent A. Busby + "We've all heard that a million monkeys
+ UNIX Systems Admin + banging on a million typewriters will
+ University of Chicago + eventually reproduce the entire works of
+ Physical Sciences Div. + Shakespeare. Now, thanks to the Internet,
+ James Franck Institute + we know this is not true." -Robert Wilensky
26 May
26 May
4:45 a.m.
Brent Busby wrote:
I wondered what the prevalent opinion was about
setting up a software
raid mirror of two sata drives under Linux LVM. This is on a 3.2GHz
quad core AMD system that almost certainly has plenty of free CPU. Will
this provide extra disk i/o that could be usefully applied to getting
more simultaneous tracks, or will using a software mirror interfere with
the RT kernel or cause latency issues/instability somewhere?
soft raid has never brought rt problems for me.
if you really want to increase your disk thoughput, you should prefer
striping (raid 0) over mirroring, though.
the only drawback is that you double the risk of data loss (if one drive
goes, all is lost). but that's ok as long as you dump the data to a safe
location every day...
then again, depending on the number of tracks you want to do, raid0 may
not even be necessary with modern sata drives.
i've been using raid1 happily for years.
5:28 a.m.
On Tuesday 26 May 2009 02:40:08 Brent Busby wrote:
I wondered what the prevalent opinion was about
setting up a software
raid mirror of two sata drives under Linux LVM. This is on a 3.2GHz
quad core AMD system that almost certainly has plenty of free CPU. Will
this provide extra disk i/o that could be usefully applied to getting
more simultaneous tracks, or will using a software mirror interfere with
the RT kernel or cause latency issues/instability somewhere?
If you want to be more dynamic with the disc allocation and still have
mirroring, consider using mirrored lvm volumes (that is lvm volumes with
mirrors, not lvm on a raid1 partition:).
For systems where it is necessary to have lots of space and have the base-
system up pretty fast after a failure, I have a small 100GB on a sw-raid1
(with ~ 3+1 disks) for / and the rest of the different disks in a lvm group to
move/resize partitions as needed. On both lvm and raid1 I had not noticed any
performance hit in real-life-applications.
BTW: I would always choose a software raid over a hardware one. That way you
can still access your raid in another machine when your current machine fails.
With hardware raid you always need a second spare hw-controller. And have to
by two new ones if the first hw-controller breaks and is no longer
manufactured...
Another note to get back on topic: ardour has its own (stripping) raid
builtin. There is an option to define multiple directories (preferable on
multiple partitions/disks) to save the soundfiles to.
Have fun,
Arnold
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participants (3)
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Arnold Krille -
Brent Busby -
Jörn Nettingsmeier